Actuator lock

ABSTRACT

An actuator lock for selectively limiting the movements of a linear actuator comprising an axially fixed lock shaft having a splined portion rotatable into and out of alignment with a correspondingly splined portion on the axially movable part of the actuator. When the splined portions on the lock shaft and axially movable part are in proper alignment with each other, the axially movable part is free to move axially relative to the lock shaft, but when the lock shaft is rotated so that the splined portions are out of alignment with each other, axial movement is limited to the axial clearance between the ends of the splined portions. The relative locations and lengths of the splined portions on the lock shaft and movable part of the actuator determine the lock positions and extent of permissible axial movement when the lock shaft is rotated to a locking position.

United States Patent Beldler 1 June 13, 1972 [54} ACTUATOR LOCK 3,576,151 4/1971 Sendoykas ..92/28 [72] Inventor. Glenn S. Beidler, Elkhart, Ind. Pflma'y Examiner Mamn P schwadron [73] Assignee: Pneumo Dynamics Corporation, C1eve- Assistant ExaminerLes1ie J. Payne l hi Attorney-Stephen M. Mihaly [22] Filed: NOV. 13, 1970 Appl' 89319 An actuator lock for selectively limiting the movements of a linear actuator comprising an axially fixed lock shaft having a 52 us. C1 ..92 17, 92 24 splifled Ponion rotatable and out alignment with a 51 int. Cl ..F15b 15/26 respondingly splined axially "Mable of {58] w of Search I I I 92/5 [7 24' 28 27 33 the actuator. When the splined portions on the lock shaft and 92/31; [88/67 axially movable part are in proper alignment with each other, the axially movable part is free to move axially relative to the 56] References Cited lock shaft. but when the lock shaft is rotated so that the splined portions are out of alignment with each other, axial UNITED STATES PATENTS movement is limited to the axial clearance between the ends of the splined portions. The relative locations and lengths of 399L082 6/1963 GFyer "92/17 the splined portions on the lock shaft and movable part of the 2597'574 5/l952 Dlckenso 92/3! X actuator determine the lock positions and extent of permissi- 2705'939 4/1955 Geyer "92/17 ble axial movement when the lock shaft is rotated to a locking 2,804,053 8/1957 Geyer ..92/1 7 position. 2,811,136 10/1957 Westcott et a1. ..92/34 X 2,886,008 5/1959 Geyer ..92/24 X 13 Claim, 7 Drawing figures ff d/ PATENTEDJUN 1 3 I872 3.668.977

SHEET 1 or 2 INVENTOR.

GLEN/V S. BE/DLER BY ATTORNEYS PATENTEDJUR 1 3 I972 SHEET 2 BF 2 INVENTOR GLEN/V S. BEIDLER BACKGROUND OF THE INVENTION This invention relates generally as indicated to an actuator lock for selectively locking or otherwise limiting the movements of a linear actuator to suit conditions.

Previously, it was known to provide linear actuators with stroke limiting devices to limit movements of the actuator in one direction as desired. However, such devices were usually relatively complex, adding considerably to the cost of the actuator, and they had to be adjusted every time it was desired to vary the stroke of the actuator, making them unsuitable for applications requiring quick response from one end position to another. There is also a need for an actuator capable of being locked in a given fixed position or multiple fixed positions, or locked out of one or more given areas but not in another area to provide different stroke limits during certain phases of operation, which is not possible with previous known actuators.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principal object of this invention to provide a relatively simple and inexpensive lock for selectively limiting the stroke of a linear actuator during certain phases of operation.

Another object is to provide a linear actuator with a lock which permits selective locking of the actuator in one or more fixed positions.

A further object is to provide a linear actuator with a lock which permits limited movement of the actuator when in the locked position.

These and other objects of the present invention may be achieved by providing the linear actuator with an axially fixed lock shaft having a splined portion rotatable into and out of alignment with a correspondingly splined portion on the axially movable part of the actuator. When the splines on the lock shaft and axially movable part are in proper alignment with each other, the axially movable part is free to move axially relative to the lock shaft, whereas when the lock shaft is rotated to bring the splined portions out of alignment with each other, axial movement is limited by engagement of the ends of the splines. To permit relative rotation between the lock shaft and movable member, the splined portion on one of the parts has one or more relieved sections of a length at least sufficient to accommodate the splined portion on the other part, and the length of the relieved sections may be varied to permit limited movements of the actuator with the locked shaft in the locked position while providing lock points at the ends of the relieved sections. By proper location of the splined portions on the lock shaft and movable part, different lock characteristics may be obtained.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. 1 is an isometric view partly in section of a linear actuator embodying a preferred form of actuator lock constructed in accordance with this invention, such actuator lock being shown in the unlocked condition permitting full extension and retraction of the actuator;

FIG. 2 is an enlarged fragmentary transverse section through the linear actuator of FIG. 1, taken on the plane of the line 22 thereof;

FIG. 3 is an enlarged fragmentary transverse section similar to FIG. 2 but showing the actuator lock in a locking position preventing linear movements ofthe actuator;

FIG. 4 is an isometric view partly in section of a linear actuator embodying a modified form of actuator lock in accordance with this invention;

FIGS. 5 and 6 are fragmentary isometric sections showing still other forms of actuator locks in accordance with this invention; and

FIG. 7 is a fragmentary longitudinal section through yet another form of actuator lock in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in detail to the drawing, and initially to FIG. 1 thereof, there is shown a linear actuator l which may be of conventional type including a cylinder 2 containing a piston 3 for reciprocation therewithin by admitting fluid pressure to one or both ports 4 and 5 at opposite ends of the cylinder. Projecting from the piston 3 is a hollow rod 6 which extends through the rod end 7 of the cylinder and has an attachment device 8 on the outboard end thereof for connection to the movable or stationary part of the device to be actuated. A suitable mount (not shown) may also be provided on the head end 10 of the cylinder for attachment to the other part of the device to be actuated.

Retraction of the rod 7 within the cylinder 2 is obtained by admitting fluid pressure to the rod end of the cylinder through the retract port 5 while exhausting the head end of the cylinder through the extend port 4. Extension of the rod 7 may be obtained by admitting pressure to the head end of the cylinder through the extend port 4 while exhausting the rod end of the cylinder.

During normal operation of the actuator I, the rod 6 may be free to move between the full retracted position with the piston 3 engaging the head end of the cylinder and the full extended position with the piston engaging the rod end of the cylinder. However, there are instances in which it may be desired to lock the actuator 1 against linear movement or restrict such linear movement to certain portions of the full stroke of the actuator during certain phases of operation, and this may be accomplished by providing the actuator with an actuator lock 11 such as shown in FIG. 1 and also in FIGS. 2 and 3. Preferably, the actuator lock 11 consists of a lock shaft 12 joumaled for rotation within the head end 10 of the actuator cylinder 2 and extending through a central opening [3 in the piston 3 into the hollow rod 6. On the free end of the lock shaft 12 which is received in the hollow rod 6, there is an externally splined land 14, and the inner wall 15 of the hollow rod 6 is correspondingly splined for mating engagement with the external splined portion 14 on the lock shaft.

With the externally splined portion 14 on the lock shaft 12 in proper alignment with the internal splines 15 on the hollow rod 6, the rod is free to move relative to the lock shaft between the fully extended and retracted positions as previously described. However, the internal splines 15 on the hollow rod 6 have relieved sections or areas 16 at one or more places along their length, each of which is ofa length at least equal to the length of the splined portion 14 on the lock shaft I2, whereby when a relieved section 16 on the hollow rod 6 is brought into axial alignment with the splined portion 14 and the lock shaft is rotated relative to the hollow rod from the FIG. 2 position to the FIG. 3 position to misalign the splines, movement of the rod 6 is restricted to the clearance space between the ends of the external splined portion 14 on the lock shaft 12 and the adjacent ends 17 and 18 of the relieved section 16. The piston rod 6 is restrained from rotating because of its connection with one of the parts of the device to be actuated.

If the axial length of the external splined portion 14 and relieved section 16 in which the external splined portion 14 is received are the same, the actuator will be locked in a given fixed position corresponding to the position of the relieved section upon rotating the external splined portion within the relieved section to the lock position at which the splined portions are out of alignment with each other. However, if the relieved section 16 is of a length greater than the length of the external splined portion 14 on the lock shaft, rotation of the external splined portion to the lock position within the relieved section will merely limit the movement of the actuator rod 6 to the relieved section. From the foregoing, it will now be apparent that different lock characteristics may readily be obtained simply by varying the location of the relieved sections or areas and also varying the relative lengths of the relieved areas and splined portions. By providing a relatively long relieved area 16 intermediate the ends of the internal splined portion 15, the actuator I may be locked out of both the full extend and full retract positions. Similarly, the actuator may be locked in the full extend or full retract positions by providing additional relieved areas 16 adjacent the ends of the internal splined portion. Thus, depending upon the number of lock areas and the sequence of rotation of the lock shaft, different stroke limits of the actuator may be obtained during different phases of operation as desired.

A similar actuator lock 1 1' may also readily be incorporated in a linear actuator 20 of the type shown in FIG. 4 including a synchronous screw shaft 21 extending into the hollow rod 22 and having a threaded connection with the piston 23. The screw shaft 21 is journaled in the head end 24 of the cylinder 25, and has a helical gear 26 mounted thereon which meshes with a worm gear 27 rotatably mounted in a transverse bore 28 in the head end of the actuator. Extending from the worm gear 27 is a rod or drive shaft 29 for connection to another actuator. A central opening 30 is provided in the synchronous screw shaft 21 for extension of the lock shaft 12' therethrough with the externally splined land 14' on the lock shaft disposed within the hollow rod 22 adjacent the free end of the synchronous screw shaftfwith the parts thus arranged, the already existing synchronous screw shafi 21 may be utilized to carry the column load of the actuator lock 11' which is transmitted directly from the splined portion 14' on the lock shaft 12' to the adjacent end of the synchronous screw shaft, permitting a relatively small diameter rod to be used for the lock shaft. Otherwise, the details of construction and operation of the actuator lock of the FIG. 4 embodiment are the same as the actuator lock of the FIG. I embodiment, and the same reference numerals followed by a prime symbol are used to identify like parts.

In the actuator lock 11 and 11 of the FIGS. 1 and 4 embodiments, the relieved splined areas are provided on the ID. of the hollow rod. However, it will be apparent that similar results may be obtained by providing a relatively short internal splined land 31 on the inner diameter of the hollow rod 32 and providing a full length external spline 33 on the lock shaft 34, with one or more relieved areas 35 on the external spline 33 at the desired lock positions for the actuator 36 as shown in FIG. 5. Locking of the actuator 36 may be obtained by rotating the lock shaft 34 to misalign the splines when the internal diameter splined land 31 on the hollow rod 32 is in axial alignment with any one of the relieved areas 35 on the external splined portion 33 of the lock shaft 34.

The splined portions 37 and 38 adjacent opposite ends of the relieved section 39 on one of the members 40 (in this case the rod) may also be out of alignment with each other as shown in FIG. 6 so that different rotational inputs will be required to the lock shaft 41 to engage each of the splined portions. Such a spline configuration may be fabricated simply by eliminating certain teeth at different locations on the splined portions 37 and 38 to make the splined portions unsymmetrical as shown, and removing certain teeth from the mating splined land 42 on the lock shaft 41. Accordingly, when the splined land 42 on the lock shaft is rotated at the relieved areas 39 into alignment with one of the splined portions 37 or 38, it will be out ofalignment with the other. and vice versa.

A two or more position lock 44 may also be provided by utilizing different spline diameters 45, 46 on different lock shafts 49 and 50 for engagement with different spline diameters 47, 48 on the hollow rod 51, as shown in FIG. 7, with separate dual or overlapping lock points 52 and 53. The smaller diameter externally splined land 45 is on the end of the inner lock shah 49 which extends through a central opening 54 in the outer lock shafi 50, and the lock shafts 49 and 50 may be rotated simultaneously or separately as desired depending on the relative positions of their respective lock points or relieved areas.

Regardless of the location and configuration of the relieved areas and splined portions on the lock shaft and hollow rod, a rotary input may be applied to the lock shaft in response to a lock signal which may consist of a hydraulic pressure signal, loss of pressure signal, mechanical or electrical signal, or other suitable means for applying a linear or rotary input to the lock shaft. Whether a rotary signal is applied to the lock shaft or a linear signal is applied to the lock shaft using a crank arrangement 55 such as shown in FIGS. 1 and 4, a rotational torque input acts on the lock shaft tending to rotate the lock shaft. If initially the actuator is not in a locking position with the relatively short splined portion in axial alignment with one of the relieved areas, the splines on both the rod and lock shaft will be loaded by the rotational torque input, whereby as soon as a lock position is reached, the lock shaft will be rotated to misalign the splines and thus engage the lock. To permit application of a linear load signal to the lock shaft when the rod is not in a locking position without causing damage to the splines, a hydraulic cylinder 56 such as shown in FIGS. 1 and 4 may be used to apply the lock signal, or a spring 57 may be used for transmitting force from the load applying device to the input shaft to limit the force applied to the lock shaft by the load applying device as further shown in FIGS. 1 and 4.

From the foregoing, it will now be seen that the various forms of actuator locks disclosed herein permit freedom of movement of the actuator when in the unlocked position and permit selective locking of the actuator in one or more fixed positions or positions of limited movement. The actuator locks are relatively simple in construction and only require the application of a rotational torque input to obtain the desired locking and unlocking of the actuator.

I, therefore, particularly point out and distinctly claim as my invention:

1. A linear actuator comprising a cylinder, a piston axially slidably received in said cylinder, a hollow rod extending from said piston through the rod end of said cylinder, and an actuator lock for selectively limiting axial movement of said rod relative to said cylinder comprising a lock shaft, means mounting said lock shaft against axial movement relative to said cylinder, said lock shaft being rotatably journaled in the head end of said cylinder, said lock shaft extending through an opening in said piston into said hollow rod, said rod and lock shaft having multi-splined portions of corresponding shape which when properly aligned and in mating engagement with each other permit axial movement of said rod relative to said cylinder while preventing relative rotation between said rod and lock shaft and when out of alignment with each other limit such axial movement, the splined portion on one of said rod and lock shaft having at least one relieved area of a length at least equal to the length of the splined portion on the other of said rod and lock shaft, and means for rotating said lock shaft relative to said rod when the splined portion on the other of said rod and lock shaft is in axial alignment with said relieved area for selectively aligning and misaligning said splined portions.

2. The linear actuator of claim I wherein there are a plurality of axially spaced relieved areas interrupting the splined portion on said one of said rod and lock shaft to provide plural lock positions for said actuator permitting rotation of the splined portion on the other of said rod and lock shaft when brought into axial alignment with any one of said relieved areas.

3. The linear actuator of claim 1 wherein said relieved area and said splined portion on the other of said rod and lock shaft are of approximately the same length, whereby when said splined portion on the other of said rod and lock shaft is rotated in said relieved area to misalign said splined portions, said rod is locked against axial movement.

4. The linear actuator of claim 1 wherein said relieved area is of a length greater than the length of the splined portion on the other of said rod and lock shaft to permit limited movement of said splined portion on the other of said rod and lock shaft between the ends of said relieved area when rotated therewithin to misalign said splined portions.

5. The linear actuator of claim 1 wherein said relieved area is on said hollow rod, and said lock shaft has a land on the free end thereof having said splined portion thereon.

6. The linear actuator of claim 1 wherein said relieved area is on said lock shaft.

7. The linear actuator of claim 1 wherein there are splined portions adjacent opposite ends of said relieved area.

8. The linear actuator of claim 7 wherein said splined portions adjacent opposite ends of said relieved area are out of alignment with each other, whereby when said splined portion on the other of said rod and lock shaft is in alignment with the splined portion adjacent one end of said relieved area, it is out of alignment with the splined portion adjacent the other end of said relieved area.

9. The linear actuator of claim 8 wherein said splined portions adjacent opposite ends of said relieved areas are of the same shape but misaligned by making such splined portions unsymmetrical at different places around their circumferential extent, and said splined portion on the other of said rod and lock shaft is of a corresponding shape to permit selective alignment and misalignment of said splined portion on said other of said rod and lock shaft with said splined portions adjacent opposite ends of said relieved area by rotating said lock shaft relative to said rod.

[0. The linear actuator of claim 1 further comprising a screw shaft journaled for rotation in said cylinder, said screw shaft extending into said hollow rod and having a threaded connection with said piston, said screw shaft having a central opening for extension of said lock shaft therethrough, said lock shaft having a land on which one of said splined portions is provided adjacent the free end of said screw shaft for direct transmission of column loads applied to said lock shaft to said screw shaft.

11. The linear actuator of claim 1 wherein said means for rotating said lock shafi comprises a hydraulic cylinder, and crank means on said lock shaft for converting the linear input of said hydraulic cylinder to a rotational torque input.

12. The linear actuator of claim 1 wherein said means for rotating said lock shaft comprises a linear input device, crank means on said lock shaft for converting the linear input to a rotational torque input, and spring means between said linear input device and crank means to limit the force applied to said lock shaft by said linear input device.

13, A linear actuator comprising a cylinder, a piston axially slidably received in said cylinder, a hollow rod extending from said piston through the rod end of said cylinder, and an actuator lock for selectively limiting axial movement of said rod relative to said cylinder comprising two lock shafts rotatably journaled in the head end of said cylinder, said lock shafts extending through an opening in said piston into said hollow rod, said rod having splined portions of difi'erent diameters, and said lock shafts having different diameter splined portions for selective alignment and misalignment with the splined portions on said rod, said splined portions on said rod and lock shafts when in mating engagement with each other permitting axial movement of said rod relative to said cylinder and when out of alignment with each other limiting such axial movement, the splined portions on one of said rod and lock shafts having at least one relieved area of a length at least equal to the length of the splined portions on the other of said rod and lock shafts to permit rotation of said lock shafts relative to said rod when the splined portions on the other of said rod and lock shafts are in axial alignment with said relieved area for selectively aligning and misaligning said splined portions, and

means for rotating said lock shafts.

* I l I i 

1. A linear actuator comprising a cylinder, a piston axially slidably received in said cylinder, a hollow rod extending from said piston through the rod end of said cylinder, and an actuator lock for selectively limiting axial movement of said rod relative to said cylinder comprising a lock shaft, means mounting said lock shaft against axial movement relative to said cylinder, said lock shaft being rotatably journaled in the head end of said cylinder, said lock shaft extending through an opening in said piston into said hollow rod, said rod and lock shaft having multi-splined portions of corresponding shape which when properly aligned and in mating engagement with each other permit axial movement of said rod relative to said cylinder while preventing relative rotation between said rod and lock shaft and when out of alignment with each other limit such axial movement, the splined portion on one of said rod and lock shaft having at least one relieved area of a length at least equal to the length of the splined portion on the other of said rod and lock shaft, and means for rotating said lock shaft relative to said rod when the splined portion on the other of said rod and lock shaft is in axial alignment with said relieved area for selectively aligning and misaligning said splined portions.
 2. The linear actuator of claim 1 wherein there are a plurality of axially spaced relieved areas interrupting the splined portion on said one of said rod and lock shaft to provide plural lock positions for said actuator permitting rotation of the splined portion on the other of said rod and lock shaft when brought into axial alignment with any one of said relieved areas.
 3. The linear actuator of claim 1 wherein said relieved area and said splined portion on the other of said rod and lock shaft are of approximately the same length, whereby when said splined portion on the other of said rod and lock shaft is rotated in said relieved area to misalign said splined portions, said rod is locked against axial movement.
 4. The linear actuator of claim 1 wherein said relieved area is of a length greater than the length of the splined portion on the other of said rod and lock shaft to permit limited movement of said splined portion on the other of said rod and lock shaft between the ends of said relieved area when rotated therewithin to misalign said splined portions.
 5. The linear actuator of claim 1 wherein said relieved area is on said hollow rod, and said lock shaft has a land on the free end thereof having said splined portion thereon.
 6. The linear actuator of claim 1 wherein said relieved area is on said lock shaft.
 7. The linear actuator of claim 1 wherein there are splined portions adjacent opposite ends of said relieved area.
 8. The linear actuator of claim 7 wherein said splined portions adjacent opposite ends of said relieved area are out of alignment with each other, whereby when said splined portion on the other of said rod and lock shaft is in alignment with the splined portion adjacent one end of said relieved area, it is out of alignment with the splined portion adjacent the other end of said relieved area.
 9. The linear actuator of claim 8 wherein said splined portions adjacent opposite ends of said relieved areas are of the same shape but misaligned by making such splined portions unsymmetrical at different places around their circumferential extent, and said splined portion on the other of said rod and lock shaft is of a corresponding shape to permit selective alignment and misalignment of said splined portion on said other of said rod and lock shaft with said splined portions adjacent opposite ends of said relieved area by rotating said lock shaft relative to said rod.
 10. The linear actuator of claim 1 further comprising a screw shaft journaled for rotation in said cylinder, said screw shaft extending into said hollow rod and having a threaded connection with said piston, said screw shaft having a central opening for extension of said lock shaft therethrough, said lock shaft having a land on which one of said splined portions is provided adjacent the free end of said screw shaft for direct transmission of column loads applied to said lock shaft to said screw shaft.
 11. The linear actuator of claim 1 wherein said means for rotating said lock shaft comprises a hydraulic cylinder, and crank means on said lock shaft for converting the linear input of said hydraulic cylinder to a rotational torque input.
 12. The linear actuator of claim 1 wherein said means for rotating said lock shaft comprises a linear input device, crank means on said lock shaft for converting the linear input to a rotational torque input, and spring means between said linear input device and crank means to limit the force applied to said lock shaft by said linear input device.
 13. A linear actuator comprising a cylinder, a piston axially slidably received in said cylinder, a hollow rod extending from said piston through the rod end of said cylinder, and an actuator lock for selectively limiting axial movement of said rod relative to said cylinder comprising two lock shafts rotatably journaled in the head end of said cylinder, said lock shafts extending through an opening in said piston into said hollow rod, said rod having splined portions of different diameters, and said lock shafts having different diameter splined portions for selective alignment and misalignment with the splined portions on said rod, said splined portions on said rod and lock shafts when in mating engagement with each other permitting axial movement of said rod relative to said cylinder and when out of alignment with each other limiting such axial movement, the splined portions on one of said rod and lock shafts having at least one relieved area of a length at least equal to the length of the splined portions on the other of said rod and lock shafts to permit rotation of said lock shafts relative to said rod when the splined portions on the other of said rod and lock shafts are in axial alignment with said relieved area for selectively aligning and misaligning said splined portions, and means for rotating said lock shafts. 